diff --git a/src/main.rs b/src/main.rs
index 5211c97..cfea471 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -51,13 +51,17 @@ struct Cli {
     #[arg(short = 'u', long, default_value_t = false)]
     ui_only: bool,
     
-    // Send UDP to what IP address (e.g. 127.0.0.1)
+    /// Send UDP to what IP address (e.g. 127.0.0.1)
     #[arg(short = 'b', long, default_value_t = std::net::IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)))]
     uip: std::net::IpAddr,
     
-    // Send UDP to what port (e.g. 8000)
+    /// Send UDP to what port (e.g. 8000; 55555 disables UDP)
     #[arg(short = 'k', long, value_parser = validate_port, default_value_t = 55555)]
     uport: u16,
+    
+    /// Spotter callsign (e.g. W1CDN)
+    #[arg(short = 's', long)]
+    spotter: String,
 }
 
 /// Convert a byte slice into a hex-dump string for debugging purposes.
@@ -358,6 +362,7 @@ fn handle_frame(frame: &AgwFrame, cli: &Cli, buffers: &mut BufferManager) {
     let source = hdr.callfrom_str();
     let basic_destination = hdr.callto_str();
     let timestamp = Local::now().format("%H:%M:%S").to_string();
+    let spotter = &cli.spotter;
 
     // Filter and compute the text from the payload only once.
     let text = filter_text(&frame.payload);
@@ -403,6 +408,7 @@ fn handle_frame(frame: &AgwFrame, cli: &Cli, buffers: &mut BufferManager) {
         let packet = json!({
             "final_destination": &final_destination,
             "source": &source,
+            "spotter": &spotter,
             "summary": &summary,
             "text": &text,
             "timestamp": SystemTime::now().duration_since(UNIX_EPOCH).unwrap().as_secs(),